Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session S28: New Ways of Seeing with ElectronsIndustry Invited Undergrad Friendly
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Sponsoring Units: FIAP Chair: Todd Brintlinger, United States Naval Research Laboratory Room: 405-407 |
Thursday, March 5, 2020 11:15AM - 11:51AM |
S28.00001: Defining Theoretical Limits of Aberration-Corrected Electron Tomography: New Bounds for Resolution, Object Size, and Dose Invited Speaker: Robert Hovden The theoretical limits of electron tomography have long been defined by the Crowther criterion, which relates 3D resolution to the number of projections acquired, and the dose fractionation theorem, which dictates total dose requirement across projections. However, these relations are invalid for aberration-corrected scanning transmission electron microscopy (STEM) where high convergence angles limit the ability to reconstruct objects larger than the depth-of-focus (c.a. 5 nm). We show overcoming the limitations of aberration-corrected STEM tomography requires collecting information beyond a traditional tilt series by acquiring a through-focal stack at every tilt. Here, information is no longer mapped to a plane in Fourier (k) space, but becomes a volumetric toroid. |
Thursday, March 5, 2020 11:51AM - 12:27PM |
S28.00002: Vibrational spectroscopy in the electron microscope Invited Speaker: Ondrej Krivanek Vibrational spectroscopy in the electron microscope (EM) has progressed remarkably since it was introduced 6 years ago (Nature 514 (2014) 209). |
Thursday, March 5, 2020 12:27PM - 1:03PM |
S28.00003: Visualizing heterogeneous nucleation with liquid cell transmission electron microscopy Invited Speaker: Taylor Woehl Heterogeneous nucleation at solid-liquid interfaces underlies a number of technologically important processes, from catalyst synthesis to fabrication of thin films, but remains poorly understood due to the dearth of techniques for quantifying nucleation energetics. In this talk, I will discuss development of a liquid cell transmission electron microscopy (LC-TEM) method for quantifying important parameters of heterogeneous nucleation, including supersaturation ratio and interfacial energy, and our efforts to utilize this approach to visualize nanoscale variations in nucleation kinetics at a solid-liquid interface. We quantify the supersaturation ratio of solute with numerical simulations of the electron beam induced chemistry during LC-TEM experiments, which enables fitting nucleation data using classical nucleation theory. Multiparticle tracking analysis applied to LC-TEM movies of nanoparticle nucleation reveals local variations in nucleation kinetics and preferential nucleation sites with nanometer scale spatial resolution. With this approach, we have demonstrated that heterogeneous nucleation of silver nanocrystals at a planar, uniform silicon nitride-water interface occurs preferentially in discrete nanoscale domains of the interface. Characterization of the solid-liquid interface with atomic force microscopy and covalent nanoparticle labeling revealed domains of surface functional groups on the interface acted as preferential nucleation sites. These results challenge previously held beliefs about nucleation on uniform interfaces, showing that nanoscale variations in surface chemistry can propagate nanoscale variations in nucleation kinetics. |
Thursday, March 5, 2020 1:03PM - 1:39PM |
S28.00004: In Situ Transmission Electron Microscopy Imaging of Nanocrystal Transformations Invited Speaker: Haimei Zheng Nanocrystals often readily change structure and morphology during growth, self-assembly and applications when interacting with their environments. It imposes challenges as well as opens opportunities for the understanding and engineering of these nanostructures for practical applications. Due to the nanometer length scale and the dynamic nature of these transformations, in situ transmission electron microscopy (TEM) has become an indispensable technique for the investigation of these processes. Recently, the significant technical advances in in situ TEM have revealed many dynamic phenomena of nanocrystals with high spatial and temporal resolution that were previously unreachable. In this talk, I will show a few examples about the structural transformations of nanocrystals during growth and self-assembly in solution. Special attention has been made to the transient states, which may draw the system outside thermodynamic equilibrium. An understanding of the nanoscale dynamics and the intermediate states aid the future design of novel materials and devices. |
Thursday, March 5, 2020 1:39PM - 2:15PM |
S28.00005: The Intersection of Cryo, Laser Ablation, and Nanoscale Electron Imaging for Intact Battery Characterization Invited Speaker: Katherine Jungjohann Characterization of intact batteries is challenging due to the great diversity of the component materials. For example, lithium anode batteries contain a stack consisting of a metal current collector, the lithium metal anode, a polymer separator saturated with lithium salts in an aprotic electrolyte, a transition metal oxide cathode, and another metal current collector. These components are generally stacked within a spring-loaded coin cell for electrochemical performance testing of the cell for repeated charge and discharge cycling. General characterization techniques require the disassembly of the stainless-steel coin cell, with analysis of each of the components individually. Here, we present a method for retaining the internal structure of the coin cell by cryogenic plunge freezing of the entire stack, followed by in-situ, athermal, ultrashort-pulse laser ablation to access the internal components in cross-section, followed by standard characterization using scanning electron microscopy and energy dispersive x-ray spectroscopy. This provides the complete structural and compositional analysis of the intact battery stack with nanometer resolution, where we have determined several failure modes of lithium metal anodes for use as rechargeable batteries. |
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